如何在 android 的 onMapReady() 中获取 onNavigationItemSelected() 值

Question

我正在尝试为导航抽屉中列出的每个项目提供位置坐标，并将其指向谷歌地图。

它如何获取我分配给 onNavigationItemSelected() 中的变量到 onMapReady() 的 lat 和 long？

//This is were I assign the coordiantes
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    double lat = 0;
    double lon = 0;

    if (id == R.id.redBuilding){
        /*lat = 13.010982;
        lon = 80.235444;

        String latitude = Double.toString(lat);
        String longitude = Double.toString(lon);
        latLong = latitude+"/"+longitude; */
    }

    if (id == R.id.nav_share) {
    } else if (id == R.id.nav_send) {
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

我想在此方法中获取分配的坐标以将其指向地图：

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
LatLng latLon = new LatLng(13.0827, 80.2707);
    mMap.addMarker(new MarkerOptions().position(latLon).title("Marker is in Chennai.").snippet("India"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLon));
}

我只使用一个活动，其中地图位于片段中。

Answer 1

如果您想更改标记，您不必使用onMapReady。您可以在初始化地图时保存标记，然后在每次用户选择项目时更改它。

private Marker marker;

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    LatLng latLon = new LatLng(13.0827, 80.2707);
    marker = mMap.addMarker(new MarkerOptions().position(latLon).title("Marker is in Chennai.").snippet("India"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLon));
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    double lat = 0;
    double lon = 0;

    if (id == R.id.redBuilding){
        lat = 13.010982;
        lon = 80.235444;

        mMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(lat, lon));
        marker.setPosition(new LatLng(lat, lon));
        marker.setTitle("your new title");
    }

    if (id == R.id.nav_share) {
    } else if (id == R.id.nav_send) {
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

Answer 2

如果 onNavigationItemSelected() 和 onMapReady() 方法都在同一个活动中，那么您可以通过将变量设为全局来轻松获取值。如果他们处于不同的活动中，那么您可以使用模型或意图。

Answer 3

@纪尧姆：

导致运行时异常：

java.lang.NullPointerException
                  at mca.annauniv.ceg.MainActivity.a(Unknown Source)
                  at android.support.design.widget.NavigationView$1.a(Unknown Source)
                  at android.support.v7.view.menu.h.a(Unknown Source)
                  at android.support.v7.view.menu.u.a(Unknown Source)
                  at android.support.v7.view.menu.j.b(Unknown Source)
                  at android.support.v7.view.menu.h.a(Unknown Source)
                  at android.support.design.internal.c$1.onClick(Unknown Source)
                  at android.view.View.performClick(View.java:4633)
                  at android.view.View$PerformClick.run(View.java:19330)
                  at android.os.Handler.handleCallback(Handler.java:733)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:157)
                  at android.app.ActivityThread.main(ActivityThread.java:5356)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:515)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
                  at dalvik.system.NativeStart.main(Native Method)